1. Field of the Invention
The present invention relates to a driving apparatus for a multiplex-winding motor having a plurality of winding groups each including windings respectively corresponding to a plurality of phases, the driving apparatus being capable of continuing to drive the multiplex-winding motor even when current detection means which detects current flowing in each winding has failed.
2. Description of the Background Art
A driving apparatus for a motor, in order to drive the motor in a desired state, detects current flowing in a winding of the motor by current detection means, to perform control to generate a voltage instruction for voltage application to the motor, and applies, to the motor, voltage based on the voltage instruction by a voltage application apparatus, thereby driving the motor.
The current detection apparatus, the voltage application apparatus, a motor winding, and the like composing the motor driving apparatus can sometimes fail, and accordingly, various methods for continuing to drive the motor even when failure occurs are proposed as disclosed in the following Patent Documents 1 to 4, for example.
That is, Patent Document 1 discloses that, in a three-phase AC electric motor, three current sensors are provided; when only one of the three current sensors has failed, current of the failed current sensor is estimated from two currents obtained from the other two current sensors that are normal, and a voltage instruction for voltage application to the three-phase AC electric motor is determined through control by a current control apparatus using the estimated current; and when two or more of the current sensors have failed, the operation is switched so as to obtain a voltage instruction from a torque instruction and a rotation angle velocity of the three-phase AC electric motor.
Patent Document 2 discloses that, in a multiphase rotary machine having a plurality of winding groups each including windings for a plurality of phases, a plurality of inverter sections each having switching means corresponding to each phase of windings are provided for the respective winding groups, and that, when OFF-failure occurs in which conduction of the switching apparatus is not allowed, in the failed inverter section which includes the switching apparatus that has failed, the switching apparatuses other than the switching apparatus that has failed in the failed inverter section are controlled based on a failure phase current instruction value calculated as a function about the rotational position of the multiphase rotary machine and a torque instruction or a function about the rotational position and a q-axis current instruction value, and a normal inverter section other than the failed inverter section is controlled in the same manner as in normal state.
Patent Document 3 discloses that, in a multiphase rotary machine having a plurality of winding groups each including windings corresponding to a plurality of phases, inverter sections of a plurality of systems, each having a leg composed of a high-potential-side switching device and a low-potential-side switching device corresponding to each phase of the multiphase rotary machine, are provided for the respective winding groups, and that, when short-circuit failure occurs in which the switching device keeps conductive state regardless of control to turn off the switching device, all the switching devices in the failed system are controlled to be OFF while the multiphase rotary machine continues to be driven by the leg in the system that does not fail, and the switching devices in the system that does not fail are controlled so as to cancel output caused along with the short-circuit failure in the failed system and operating against the drive of the multiphase rotary machine, or so as to reduce the influence of the output on the driving.
Patent Document 4 discloses an electric power steering apparatus which assists steering force of a driver by using driving force for an electric motor, the electric power steering apparatus including: a control apparatus which sets a current instruction value needed for the driving force of the electric motor; a plurality of power converters; a plurality of groups of windings, corresponding to the plurality of power converters, which generate the driving force of the electric motor by being respectively supplied with current from the plurality of power converters; and a failure detection apparatus which detects failure of the power converter or the winding. When the failure detection apparatus has detected failure, the current instruction value is reduced from that in normal state, and current is continuously supplied from the normal one of the power converters to the corresponding windings.    Patent Document 1: Japanese Patent No. 2861680    Patent Document 2: Japanese Laid-Open Patent Publication No. 2011-78221    Patent Document 3: Japanese Laid-Open Patent Publication No. 2011-78230    Patent Document 4: Japanese Laid-Open Patent Publication No. 2011-131860
The conventional techniques disclosed in the above Patent Documents 1 to 4 have the following problems.
That is, Patent Document 1 proposes a method for, in the three-phase AC electric motor, continuing to drive the motor when the current detection apparatus has failed, but does not disclose any measure for the case where the current detection apparatus has failed in a multiplex-winding motor.
In Patent Documents 2 to 4, voltage application apparatuses such as a plurality of inverters are provided for the respective winding groups of the multiplex-winding motor, whereby, even if some of the motor windings or the voltage application apparatuses have failed, the motor can continue to be driven by the other normal motor windings and voltage application apparatus. However, they do not disclose any control method for the case where the current detection apparatus has failed.